lii. PRESIDENT'S ADDRESS. 



Cestracioniidtv. Dorsal fins, armed with a spine. Dentition 

 adapted for the prehension and mastication of crustaceous and 

 hard-shelled animals. This family is one of particular interest, 

 it occurs in the Palaeozoic and Mesozoic Beds. It is represented 

 at the present day by the Port Jackson Shark, Cestracion phtlippi, 

 which throws much light on the dentition of its fossil prede- 

 cessors. This Shark is harmless, its food consisting of 

 Crustaceans and shell-fish. After death the teeth are easily 

 detached from the jaws. Four species are known from Japan, 

 Amboyna, Australia, the Galapagos Islands, and California. 



Lamnidce. These made their first appearance in the Carbon- 

 iferous Age. The majority of the family are found in the 

 Cretaceous and Tertiary Beds. 



The fossil-remains of fish, which have excited more attention 

 than any others, are the large bony spines called Ichthyodorulites, 

 which appear to have been those of the anterior part of 

 the dorsal-fin of Elasmobranchii. The earliest genus is Onchus, 

 from the Silurian bone-bed of Ludlow. Ichthyodorulites are 

 found in most of the geological beds from the Palaeozoic to 

 the Pliocene. At the close of the Jurassic age they began 

 to decline, appearing in small numbers in the chalk, notably 

 in the chalk at Lewes. Agassiz relegates them to the 

 genera Hybodus, Spinax, Chimaera, and Ptychodus. They are 

 often associated with the teeth of Sharks, but as it cannot be 

 irrefutably proved to which species they belong, this distin- 

 guished naturalist gives a generic name to each. 



Lamnidae. Owing to the variety in the shape of the teeth in 

 different parts of the same mouth, a satisfactory determination of 

 species is impossible. 



Lamna (Oxyrhina) " The Porbeagles" Of the three living 

 species, L. cornulicus is the best known ; it frequently strays to 

 the British coast. It is carnivorous, feeding chiefly on fishes. 

 Our Hon. Secretary has a specimen of this Shark in his Museum 

 at Montevideo caught in the West Bay. 



Scyllidw. The common " Dog-fish " of our coast. Frequents 

 the seas of the temperate zones. It was found by the Challenger 



